Go-karts are motor vehicles that are used for leisure and sporting activities. In go-karts, a chain is usually used to transmit power from the engine to the rear-wheel drive shaft; this chain is routed around a engine pinion and a sprocket that is mounted on the rear-wheel drive shaft. In order to achieve the large reduction ratio that is needed by using this single-stage chain drive, it is necessary to make the engine pinion extremely small (tooth count: 9–11). For technical reasons, smaller pinions cannot be made. On the other hand, there is a limit to the extent to which the driven sprocket on the rear-wheel drive shaft can be made larger because of the low ground clearance of the vehicle. If the driven sprocket is too large, it will hit the ground. The chain is exposed, i.e., it is not protected by a chain guard. The chain is lubricated manually, at more or less regular intervals.
Such extreme operating conditions, combined with the high speed at which the chain moves—modern go-kart engines run at speeds of up to 21,000 rpm—place extremely high stresses on the chain drive system and these are linked to high rates of wear, a rapid loss of efficiency, short service life, and excessive noise. The outcome is that the chain, which is costly in and of itself, as well as the sprocket, have to be replaced at very short intervals.
CH 590149 A and FR 2302000 A (and similarly GB 2 212 464 A) propose that the chain drive be replaced by spur gearing in order to eliminate the problems referred to above. If this is done, the spur gearing forms a drive unit that is separate from the engine and is enclosed, at least partially, by its own housing. In order to match the reduction ratios to various driving conditions, at least one of the gear wheels can be replaced by another having a greater or smaller tooth count. The engine is installed on a mounting plate in such a way that it can be moved and thereby compensate for the differences in the diameters of the gear wheels that result from such an installation.
One disadvantage with this concept is that it is extremely difficult to achieve the precise alignment of two spur gears that mesh with each other, which is necessitated by such gearing, if the variable engine installation concept that has been proposed is used. Small misalignments inevitably lead to greater stresses, increased wear, and to even more noise.
An additional disadvantage is the fact that complete encapsulation of the transmission is difficult because of the separation of the engine from the transmission, and because of the variable engine mounting; in addition, an installation of this kind makes it almost impossible to avoid oil leaks.